Current finite linear motion guide units of the sort recited just above have been used extensively in diverse fields of machinery such as semiconductor manufacturing machines, which are seeing growing demands for high working performance including high-speed operation, high acceleration/deceleration, highly slim in construction, high accuracy and low resistance in sliding movement, and so on. Most of the finite linear motion guide units with means for keeping the cage against wandering have been conventionally models for small-sized machines. Nevertheless, modern industries are in need of larger versions of the finite linear motion guide units of the same type to be suited for large-sized machines.
In the commonly assigned Japanese Patent Laid-Open No. 2004-197850, there is disclosed a finite linear motion guide unit in which the cage with hook hole lies between the guideway members while the pinion holder is inserted into the hook hole in the cage after once having been made deformed in itself, and then released from the deforming stress to fit into the hook hole to come into engagement with the cage. Next, the pinion shaft is forced into the bearing recess in the pinion holder to carry the pinion for rotation. With the finite linear motion guide unit constructed as stated earlier, the cage lying between the guideway members to space the rolling elements from each other is installed therein with the pinion holder, which fits into the hook hole in the cage in a simple snap-fit manner to provide the tiny construction to keep the cage against wandering. To this end, the pinion holder has a flange extending out of any side of the pinion holder so as to come into abutment against any one surface of an edge around the hook hole, and an snap hook extending out of the other side of the pinion holder to come into engagement with another surface of the edge around the hook hole.
Another finite linear motion guide unit is disclosed in the commonly assigned Japanese Patent Laid-Open No. 2003-28157, in which the rack-and-pinion arrangement is interposed between paired guide rails to keep a cage retaining more than one rolling element therein against falling off from the guide rails. The pinion holder is installed closely in the aperture in the cage and further fastened to the cage in a way some pins on the flange portion of the pinion holder are forcibly pushed into the holes of the cage, and then caulked at their opposite ends by any suitable tool. The pinion is held in the pinion holder, with the pinion shaft being carried for rotation in bearing areas in the pinion holder.
A further another commonly assigned Japanese Patent Laid-Open No. H07-91445 disclosed a finite linear motion guide unit that is envisaged realizing positive control of the relative travel of the guideway members. With the finite linear motion guide unit recited just earlier, the guideway members are arranged in parallel with one another in such a geometric relation that their raceway grooves are in opposition to each other while the racks are placed in the relief valleys cut deep in the raceway grooves. Between the confronting guideway grooves, there are placed all the cylindrical rollers and the pinion that comes into mesh with the rack. With the finite linear motion guide unit stated just above, the pinion is held for rotation between the upper and lower pinion holder portions, whose shapes are triangular in transverse section. Upon installation of the pinion into the cage, the upward top of the upper pinion holder portion is first fit into the V-notch cut in the edge bordering around the aperture in the cage and then the downward bottom of the lower pinion holder portion is forcibly snapped into the V-notch in the edge bordering around the aperture in the cage while getting the edge deformed elastically.
The finite linear motion guide unit disclosed in the Japanese Patent Laid-Open No. 2004-197850 recited earlier, although but well suited for the small construction in size, is not ready for large construction because the pinion holder is inevitably rendered too large in size to make the pinion holder for itself deformable. With the finite linear motion guide unit made large in construction, moreover, as the effort exerted on the pinion to keep the cage against wandering could become large, there are still issues to be worked out in, especially, appliances that need to securely bear the pinion in the pinion holder.
With the finite linear motion guide unit disclosed in the Japanese Patent Laid-Open No. 2003-28157, the installation of the pinion holder in the cage needs a plurality of pins and, therefore, several chores in assembly and in working of the parts or components. The prior finite linear motion guide unit, when adapted for the large machines, needs to consider that it takes more force loaded on the pinion to keep the cage against wandering. Thus, there are still issues to be worked out in, especially, appliances that need to securely bear the pinion in the pinion holder.
With any of the prior finite linear motion guide units recited earlier, as the pinion holder is retained in place by just any mating edges of the cage, the pinion holder has to be firmly secured to the cage in preparation for their applications to the large machines. The prior finite linear motion guide units, when designed for the large machines, needs to consider that it takes more force loaded on the pinion to keep the cage against wandering. Thus, there are still issues to be worked out in, especially, appliances that need to securely bear the pinion in the pinion holder.